How to Make Boat Stabilizers

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Boat stabilizers are floats attached to the sides of a boat or canoe that add buoyancy and aid in preventing the craft from capsizing. While outriggers, as those used on native canoes, provide the same functions, they are much more cumbersome and awkward when mooring and maneuvering close to other objects. Boat stabilizers are often bladders or other inflatables attached to permanent boat connections. A DIY set of boat stabilizers can be easily constructed of polyurethane foam inside a pair of waterproof fabric tubes, connected to an attachment board.

Items you will need

  • 60-inch vinyl-covered marine fabric

  • Tape measure

  • String

  • Permanent marker

  • Scissors

  • Sewing machine

  • 2-by-12-inch treated pine lumber

  • Circular saw

  • Power drill

  • Hammer and nails

  • 2-by-4-inch treated pine lumber

  • 3-inch wood screws

  • Utility knife

  • Carpenter's spring clamps

  • Canned closed-cell polyurethane spray foam

  • 3-inch machine bolts

Step 1

Use a tape measure, framing square and a permanent marker to measure and mark two 10-foot lengths of 60-inch heavy vinyl-covered marine fabric.

Step 2

Use shears or heavy scissors to cut the two pieces of vinyl.

Step 3

Fold a piece of the vinyl-coated fabric lengthwise. Run it through a sewing machine at low speed with a denim-grade nylon thread, stitching the long-side edges together 1/2 inch from the edge. Repeat the process, using the first seam as a guide, and stitch a second, parallel seam 3 inches inboard of the original seam. Repeat this process on the other fabric.

Step 4

Sew a seam along both ends (the short edges) of the two fabric tubes, 1/2 inch in from the edge.

Step 5

Measure, mark and cut an 8-foot length of 2-by-12 treated pine lumber with a circular saw. Mark drill holes in the flat side of the board, 2 inches from the edge and located 1, 4 and 7 feet from one end. Use a power drill to drill 1/2-inch holes at these three drill hole locations. Repeat this operation, producing a second identically cut and drilled 2-by-12 board.

Step 6

Lay one of the 2-by-12 boards flat and pointing away from view, with the line of holes on the right side. Lay one of the vinyl-fabric tubes on and along the board with the seam on the left side and an equal amount of the excess length of the fabric hanging over each end. Tack one end of the tube to the board with a nail and hammer, and the edge of the seam 2 inches inbound from the edge of the board. Make that nail point at 14 inches down from the upper end of the fabric tube. Repeat this nailing process at the bottom end of the board/tube, stretching the tube taught before nailing. Repeat this attachment process on the other board.

Step 7

Lay a piece of 2-by-4 treated lumber 8 feet long over the tacked seam on the board and drive seven 3-inch wood screws through the 2-by-4 and fabric, and into the 2-by-12. Make these screw locations at equidistant points along the 8-foot board. Repeat this process with the other fabric tube, on the other board.

Step 8

Use a utility knife to cut a 1/2-inch hole in both ends of the fabric tubes. Clamp one hole closed with a spring clamp. Insert the head of the closed-cell polyurethane spray foam can and fill the tube half full with foam. An apparent half-full appearance is appropriated, since the foam will expand. Clamp that hole and remove the other-end clamp and spray foam liquid, if needed, into that end of the tube. Allow the foam to cure for 24 hours.

Step 9

Measure, mark and drill 1/2-inch holes in the upper gunnel of the boat using the tube-attached 2-by-12 board as a template. Drill the holes and bolt the board to the boat gunnel with 3-inch machine bolts. The height of the board — how high it rides in the water — will vary but the stabilizer should be half submerged when the boat is at full capacity. Repeat this process, connecting the other stabilizer to the other side of the boat.


  • Wear goggles and gloves when using polyurethane foam.
  • Use caution when using power tools.